A significant portion of the spacecraft currently in orbit around the Earth are currently in need of servicing, or will be in the near future. The servicing needed may include propellant resupply, cleaning of solar panels, replacement or repair of various onboard equipment, or other servicing known in the art. These spacecraft are non-cooperative systems, which means that they are not designed to facilitate the servicing, docking or coupling with other space vehicles once on orbit.
There currently exists a technique of docking an extension spacecraft to a non-cooperative satellite for extending the life of that satellite. The extension spacecraft is designed specifically for that particular satellite, is permanently attached to that satellite, and has guidance, navigation, and controls for controlling all proximity operations with the satellite, as well as station keeping the resulting spacecraft-satellite combination. The extension spacecraft contains onboard propellant that is used by the extension spacecraft in performing all of the stated maneuvers. As such, the extension spacecraft concept is limited to one satellite and has limited use beyond this. The extension spacecraft is limited to controlling and adjusting the attitude and position of the spacecraft-satellite combination. Also, note that the satellite, the extension spacecraft, and the spacecraft-satellite combination remain in the satellites orbital position and are non-cooperative.
Another technique currently exists for launching into orbit a mothership vehicle that contains multiple operational service vehicles. Each of the operational service vehicles has a service module and a command module, which is attached and fixed to the service module. The service module has propellant, thrusters, and attitude control. The command module has target location/tracking/inspection sensors and robotic arms and grippers for performing service tasks. The operational service vehicles perform intricate tasks such as extending solar array panels or reorienting antennas. The stated vehicles are also limited in their use. The stated vehicles are limited in the amount of time they can operate away from the mothership, in their ability to replace spacecraft propellant and in their ability to provide a reliable or fixed connection with a spacecraft being repaired.
The above-stated extension spacecraft and service vehicles are also limited to single satellite service missions. Thus, for each spacecraft to be repaired a service vehicle must be launched into space. The associated costs, time, and efforts associated with each launch are substantial.
A significant portion of the satellites currently in orbit are spin-stabilized satellites. Docking with spinning satellites can be technically problematic. It is difficult to accurately position and adjust attitude angles and speed and angular velocity of servicing vehicles to align with the spin-stabilized satellites. A mismatch in alignment can cause a collision-like reaction. Thus, the spin-stabilized satellites are non-cooperative by their spinning nature alone. The remaining satellites are body stabilized satellites. Although easier to dock with, body stabilized satellites may also be non-cooperative.
Thus, there exists a need for a spacecraft that is capable of performing in-space service techniques, that overcomes the above-stated limitations, and that can be adjusted to safely and reliably dock with and service a variety of non-cooperative, cooperative, spin-stabilized, and body stabilized spacecraft.